“A senior official said Trump mocked Rosenstein’s recent testimony on Capitol Hill, saying he looked weak and unable to answer questions.” Trump has even claimed Rosenstein is a “Threat to his presidency.”
Perhaps most absurdly, Trump has attacked Rosenstein as a Democrat. It was Rosenstein who pushed back on Republicans last week during the House Judiciary Committee hearing, as they relentlessly attacked Mueller’s investigation as being tainted, unfair, and out of control.
Rosenstein insisted he saw no reason to take any action against Mueller. Instead, the Republican special counsel has Rosenstein’s full confidence.
If the White House does get desperate enough and decides to move against Mueller, the way the White House desperately moved to fire Comey last May, Trump would have to demand that Rosenstein take up the task of firing the special prosecutor.
Mueller can only be removed from his role if Rosenstein found “Good cause.” If he did not find good cause, Trump would have to fire him and likely others inside the Department of Justice leadership until he found someone willing to complete the White House’s command to get rid of Mueller.